Service recovery method, apparatus, and system for a wireless communication network

ABSTRACT

A service recovery method and a device for a wireless communication network are disclosed. In an embodiment, the method includes receiving, by a target base station, a radio resource control (RRC) re-establishment request from a terminal and sending, by the target base station, an indication message indicating a radio link failure to a source base station to trigger the source base station with self-determination to initiate a handover preparation procedure between the source base station and the target base station, wherein the terminal remains in an active state.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/282,988, filed on Oct. 27, 2011, which is a continuation ofInternational Application No. PCT/CN2009/071479, filed on Apr. 27, 2009.All of the afore-mentioned patent applications are hereby incorporatedby reference in their entireties.

TECHNICAL FIELD

The present invention relates to wireless communications technologies,and in particular, to a service recovery method, apparatus, and systemfor a wireless communication network.

BACKGROUND

During running of a mobile network, a cell may suddenly encounter afault or a power failure. In this case, the cell cannot work properly,and a service of a user equipment (UE) in an active state isinterrupted. When the cell suddenly encounters a fault and fails to workproperly, the UE detects a Radio Link Failure (RLF), reselects a newcell, and then initiates a link re-establishment process of a radiolink.

In implementation of the present invention, the inventor finds that, inthe prior art, when the cell encounters a fault, after the UE selects anew cell, no technical scheme about how an access network device in thenew cell establishes a connection with a core network is provided, andtherefore service continuity of the UE in the active state cannot beguaranteed.

SUMMARY

An embodiment of the present invention provides a service recoverymethod for a wireless communication network. The method includes:receiving a radio resource control (RRC) re-establishment request or acell update message from a UE; performing an RRC establishment processthat is triggered by a non-access-stratum (NAS) of the UE if the RRCre-establishment or the cell update fails; and sending an initial UEmessage to a core network device after the RRC establishment process iscomplete.

Another embodiment of the present invention provides a service recoverymethod for a wireless communication network. The method includes:receiving an RRC re-establishment request or a cell update message froma UE; and sending a notification message to a source evolved NodeB (eNB)to request the source eNB to initiate a switching preparation process ofan X2 and/or S1 interface if context information of the UE cannot beobtained.

Another embodiment of the present invention provides a service recoverymethod for a wireless communication network. The method includes:receiving an RRC re-establishment request or a cell update message froma UE; obtaining context information of the UE; and sending anotification message to a core network device to request forestablishing a connection with the core network device.

Another embodiment of the present invention provides a service recoveryapparatus for a wireless communication network. The apparatus includes:a receiving unit, configured to receive an RRC re-establishment requestor a cell update message from a UE; an RRC establishing unit, configuredto perform an RRC establishment process that is initiated by an NAS ofthe UE when the RRC re-establishment or the cell update fails; and aprocessing unit, configured to send an initial UE message to a corenetwork device when the RRC establishment process is complete.

Another embodiment of the present invention provides a service recoveryapparatus for a wireless communication network. The apparatus includes:a receiving unit, configured to receive an RRC re-establishment requestor a cell update message from a UE; and a notifying unit, configured tosend a notification message to a source access network device to requestthe source access network device to initiate a switching preparationprocess of an X2 and/or S1 interface when context information of the UEcannot be obtained.

Another embodiment of the present invention provides a service recoveryapparatus for a wireless communication network. The apparatus includes:a receiving unit, configured to receive an RRC re-establishment requestor a cell update message from a UE, where the RRC re-establishmentrequest or the cell update message contains context information and/oran identifier of the UE; an obtaining unit, configured to obtain thecontext information of the UE; and a sending unit, configured to send anotification message to a core network device to request forestablishing a connection with the core network device.

Another embodiment of the present invention provides a service recoverysystem for a wireless communication network. The system includes a corenetwork device and the service recovery apparatuses for the wirelesscommunication network as provided in the preceding.

The preceding technical solutions provided in embodiments of the presentinvention target a process of establishing a connection between theaccess network device serving a new cell and the core network deviceduring reselection of a UE to the new cell for service recovery when acell cannot work properly in the case of an emergent fault, therebyensuring service continuity of the UE in the active state.

BRIEF DESCRIPTION OF THE DRAWINGS

To better illustrate technical solutions in embodiments of the presentinvention or in the prior art, the following briefly describes theaccompanying drawings that need to be used in descriptions about theembodiments. It is apparent that the accompanying drawings merelyprovide some embodiments of the present invention. Those skilled in theart may obtain other accompanying drawings based on these accompanyingdrawings without creative efforts.

FIG. 1 is a schematic diagram of coverage of cells within differentsystems;

FIG. 2 is a schematic structural diagram of a Long Term Evolution (LTE)system;

FIG. 3 is a schematic diagram of a structure between an LTE system and aUniversal Mobile Telecommunications System (UMTS) or a Global System forMobile communication (GSM) system;

FIG. 4 is a schematic diagram of a service recovery process according toa first embodiment of the present invention;

FIG. 5 is a schematic diagram of a first service recovery processaccording to a second embodiment of the present invention;

FIG. 6 is a schematic diagram of a second service recovery processaccording to the second embodiment of the present invention;

FIG. 7 is a schematic diagram of a service recovery process according toa third embodiment of the present invention;

FIG. 8 is a schematic diagram of a service recovery process according toa fourth embodiment of the present invention;

FIG. 9 is a schematic diagram of a service recovery process according toa fifth embodiment of the present invention;

FIG. 10 is a schematic diagram of a service recovery process accordingto a six embodiment of the present invention;

FIG. 11 is a structural block diagram of a first service recoveryapparatus according to a seventh embodiment of the present invention;

FIG. 12 is a structural block diagram of a second service recoveryapparatus according to the seventh embodiment of the present invention;

FIG. 13 is a structural block diagram of a first service recoveryapparatus according to an eighth embodiment of the present invention;

FIG. 14 is a structural block diagram of a second service recoveryapparatus according to the eighth embodiment of the present invention;and

FIG. 15 is a structural block diagram of a service recovery apparatusaccording to a ninth embodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The technical solutions in the embodiments of the present invention areelaborated below with reference to the accompanying drawings. Evidently,the embodiments described below are for an exemplary purpose only,without covering all embodiments of the present invention. Those skilledin the art may derive other embodiments from the embodiments givenherein without making any creative effort, and all such embodiments arecovered in the protection scope of the present invention.

In a mobile communication system, to ensure service continuity or solvea coverage problem, cells within different systems or at differentfrequencies may generally cover the same area. As shown in FIG. 1, cellA in an LTE system and cell A′ in a UMTS system cover the same area.

FIG. 2 shows a network structure of an LTE system. An interface betweena core network device Mobility Management Entity (MME) and an eNB is anS1 interface. An interface between different MMEs is an S10 interface.An interface between different eNBs is an X2 interface. An interfacebetween an eNB and a UE is a Uu interface. The Uu interface uses an RRCmessage for communication.

FIG. 3 shows a connection between an LTE system and a UMTS/GSM system.An interface between an access network device Radio Network Controller(RNC) or Base Station Controller (BSC) and a core network device ServingGPRS Support Node (SGSN) is an Iu or A interface. An interface betweenan MME and an SGSN is an S3 interface.

The embodiments of the present invention provide a process ofestablishing a connection between an access network device serving a newcell and a core network device when a cell in the LTE system is faultyand a UE reselects the new cell, where the new cell may be a cell in theLTE system or a cell within a different system, such as a UMTS cell or aGSM cell.

Embodiment 1

This embodiment provides a service recovery method for a wirelesscommunication network, as shown in FIG. 4. This method includes:

Step 11: An access network device serving a new cell receives an RRCre-establishment request or a cell update message from a UE.

When detecting an RLF, the UE reselects a new cell, and sends the RRCre-establishment request to an eNB serving the new cell. This new cellmay be an LTE cell, a UMTS cell, or a GSM cell. The access networkdevice in the LTE cell is an eNB. The access network device of the UMTSor GSM cell is an RNC or a BSC. When the new cell is the LTE cell, theUE sends the RRC re-establishment request. When the new cell is a UMTSor GSM cell, the UE sends the RRC re-establishment request or the cellupdate message.

Step 12: If the access network device in the new cell does not findcontext information of the UE, send a corresponding RRC re-establishmentfailure message or a cell update failure message, or do not send anymessage to the UE.

Step 13: Perform an RRC establishment process that is triggered by anNAS, where the RRC establishment process is triggered by the NAS of theUE. If the UE receives a failure message or does not receive any messagewithin a set period, the NAS triggers a link connection with the newcell. Alternatively, in the RRC establishment process, an RRC messagefrom the UE may carry an indication or a cause value, where theindication or the cause value is configured to indicate that the RRCestablishment process is a link recovery process triggered by the NAS.

Step 14: Send an initial UE message to a core network device after theRRC establishment process is complete. For the LTE cell, this corenetwork device is an MME. For the UMTS or GSM cell, this core networkdevice is an SGSN.

In this embodiment, a connection between the eNB serving the new celland the core network device is established through the initial UEmessage, thereby ensuring service continuity of the UE in an activestate.

Embodiment 2

This embodiment provides a service recovery method for a wirelesscommunication network. In this embodiment, when a new cell reselected bya UE is a cell in an LTE system, an access network device in the newcell in this embodiment is an eNB serving the new cell, that is, a neweNB. As shown in FIG. 5, the method includes:

Step 101: When detecting an RLF, a UE reselects a new cell and sends anRRC re-establishment request to an eNB (a new eNB) in the new cell.

Step 102: After receiving the RRC re-establishment request, the new eNBsends an RRC re-establishment failure message if UE context is notfound.

Step 103: An NAS of the UE triggers an RRC establishment process. Afterthe triggering performed by the NAS, the new eNB and the UE perform theRRC establishment process. Alternatively, in the RRC establishmentprocess, an RRC message from the UE may carry an indication or a causevalue, where the indication or the cause value is configured to indicatethat the RRC establishment process is a link recovery process triggeredby the NAS.

Step 104: After RRC establishment is complete, the new eNB sends aninitial UE message to an MME to trigger establishment of an S1interface. For example, after receiving an RRC establishment completemessage from the UE, the new eNB sends the initial UE message to the MMEto trigger establishment of the S1 interface. This step implements aconnection between the eNB and the MME through the initial UE message.

Step 105: The new eNB receives an initial context establishment requestfrom the MME.

Step 106: A security authentication process is performed between the UEand the new eNB. In this process, the new eNB may obtain contextinformation of the UE. This step is optional.

Step 107: The new eNB and the UE perform RRC re-configuration.

Step 108: The new eNB sends an initial context establishment response tothe MME.

Steps 105 to 108 are the same as those in an existing normal servicerequest process.

Alternatively, step 109, in which the MME sends an S1 interface releasecommand to a source eNB to instruct the source eNB to release the S1interface, may be included after step 108. Many methods exist forreleasing the S1 interface of the source eNB. Releasing the S1 interfaceaccording to the S1 interface release command is only one of themethods. Therefore, the present invention is not confined to thismethod, for example, the S1 interface between the MME and the source eNBmay also be released in a timing manner by triggering a timer.

In another embodiment of the present invention, if the MME connected tothe eNB serving the new cell is changed, that is, a new MME connected tothe new eNB is not a source MME connected to the source eNB, the twoMMEs transfer a message through an S10 interface. That is, the new MMEsends a message of instructing the source eNB to release the S1interface to the source MME through the S10 interface, and then thesource MME instructs the source eNB to release the S1 interface.

In the preceding embodiment, the new eNB completes establishment of theS1 interface by initiating an originating service process, for example,the initial UE message.

In another embodiment of the present invention, if the new cell is aUMTS or GSM cell, an access network device RNC or BSC in the UMTS or GSMcell corresponds to the new eNB in the preceding embodiment, an Iu or Ainterface corresponds to the S1 interface in the preceding embodiment,and an SGSN corresponds to the new MME. In this case, the RNC or BSC maysend an initial UE message of the Iu or A interface to establish the Iuor A interface. As shown in FIG. 6, taking that the new cell is a UMTScell as an example, the service recovery method in this embodimentincludes the following steps:

Step 201: When detecting an RLF, the UE reselects a new cell and sendsan RRC re-establishment request or a cell update message to an RNC (anew RNC) of the new cell. Alternatively, a timer may be started at thesame time.

Step 202: After receiving the RRC re-establishment request or the cellupdate message, the RNC sends an RRC re-establishment failure message ora cell update failure message, or does not send any message if the RNCdoes not find UE context.

Step 203: An NAS of the UE triggers an RRC establishment process. Afterthe UE receives the failure message or does not receive any messageafter the timer expires, the NAS triggers link establishment with thenew cell, and the new RNC and the UE perform the RRC establishmentprocess. Alternatively, in the RRC establishment process, an RRC messagefrom the UE may carry an indication or a cause value, where theindication or the cause value is configured to indicate that the RRCestablishment process is a link recovery process triggered by the NAS.

Step 204: After RRC establishment is complete, the new RNC sends aninitial UE message to a new SGSN to trigger establishment of an Iuinterface. For example, after the new RNC receives an RRC establishmentcomplete message, the UE sends an initial direct transmission message tosubmit a service request; the new RNC sends the initial UE message tothe new SGSN through the Iu interface to trigger establishment of the Iuinterface.

Step 205: The new SGSN sends a downlink direct transmission message tothe UE, and the new RNC forwards this message that is used as a responseto the service request.

Step 206: The new RNC and the UE perform a security authenticationprocess. This step is optional.

Step 207: The new SGSN sends a Radio Access Bearer (RAB) assignedrequest message to the new RNC.

Step 208: The new RNC and the UE establish an RAB.

Step 209: The new RNC sends an RAB assigned response message to the newSGSN.

Steps 204 to 209 are the same as those in the existing normal servicerequest process.

Alternatively, after step 209, the method may further include:

Step 210: The new SGSN sends an S1 interface release command through anS3 interface to a source MME.

Step 211: The source MME sends the S1 interface release command to asource eNB.

In this embodiment, the RNC in the new cell completes establishment ofthe Iu interface with the core network device SGSN in the new cellthrough the initial UE message, thereby ensuring service continuity ofthe UE in the active state.

In a GSM system, similarly, the BSC completes establishment of the Ainterface with the SGSN through a first A interface message in a normalservice establishment process.

Embodiment 3

This embodiment provides a service recovery method for a wirelesscommunication network. In this embodiment, taking that a new cell is anLTE cell as an example, an access network device in the new cell in thisembodiment is an eNB serving the new cell, that is, a new eNB. As shownin FIG. 7, this method includes:

Step 301: A UE finds an RLF, reselects a new cell, and sends an RRCre-establishment request to a new eNB.

Step 302: After receiving the RRC re-establishment request, the new eNBsends an RRC re-establishment failure message to the UE if UE context ofthe UE is not found.

Step 303: After the UE receives the RRC re-establishment failuremessage, an NAS triggers a process of establishing RRC with the new eNB.After the triggering performed by the NAS, the new eNB and the UEperform the RRC establishment process. Alternatively, in the RRCestablishment process, an RRC message from the UE may carry anindication or a cause value, where the indication or the cause value isconfigured to indicate that the RRC establishment process is a linkrecovery process triggered by the NAS.

Step 304: The new eNB sends a notification message to a source eNB torequest the source eNB to initiate a switching preparation process of anX2 interface and/or an S1 interface. The method of sending thenotification message by the new eNB to the source eNB includes: directlysending the notification message to the source eNB through the X2interface; or sending the notification message to an MME through the S1interface, and forwarding, by the MME, the notification message to thesource eNB. That is, the source eNB is instructed to initiate theswitching preparation process of the X2 or S1 interface in a directmanner or in an indirect manner.

After receiving the notification message, the source eNB initiates theswitching preparation process of the X2 or S1 interface. That is, afterreceiving the notification message from the X2 interface of the new eNBor from the S1 interface of the MME, the source eNB performs theswitching preparation process of the X2 or S1 interface. After theswitching preparation process is complete, an S1 interface connectionbetween the eNB serving the new cell and a new MME is established. Theswitching preparation process of the X2 or S1 interface is implementedby using the prior art, and therefore is not described in thisembodiment. Alternatively, before initiating the switching preparationprocess of the X2 or S1 interface, the source eNB may send a responsemessage to the eNB serving the new cell.

In step 304 of this embodiment:

If the new eNB does not know a running status of the source eNB, and anX2 interface exists between the new eNB and the source eNB, anotification message is sent to the source eNB through the X2 interface,and a timer may be started at the same time. If the X2 interface of thenew eNB does not receive a response message within a specified timeperiod or receives a failure message, the new eNB sends a notificationmessage to the MME through the S1 interface. The MME transfers thisnotification message to the source eNB through the S1 interface torequest the source eNB to initiate the switching preparation process ofthe X2 and S1 interfaces.

If the MME connected to the eNB serving the new cell is different fromthat connected to the source eNB, that is, the new eNB is connected to anew MME, and the source eNB is connected to a source MME, the new eNBsends a notification message to the new MME through the S1 interface,the new MME transfers this notification message to the source MMEthrough an S10 interface, and the source MME forwards this notificationmessage to the source eNB to request the eNB to initiate the switchingpreparation process of the S1 interface.

If the new cell is a UMTS or GSM cell, the access network device in thenew cell is an RNC or BSC that corresponds to the preceding eNB servingthe new cell, the Iu or A interface corresponds to the preceding S1interface, and a core network device SGSN in the new cell corresponds tothe preceding new MME. The access network device RNC or BSC in the newcell sends a notification message of the Iu or A interface to the sourceeNB through the SGSN and the source MME to request the source eNB toperform the switching preparation process of the S1 interface. A messagethat is sent to the new cell after the UE detects an RLF may be an RRCre-establishment or a cell update message. Specifically, the RNC or BSCsends a notification message to the SGSN through the Iu or A interface.The SGSN sends the notification message to the source MME through an S3interface. The source MME forwards the notification message to thesource eNB through the S1 interface to instruct the source eNB toperform the switching preparation process of the S1 interface. Afterreceiving the notification message, the source eNB performs theswitching preparation process of the S1 interface to establish an Iu orA interface connection between the RNC or BSC serving the new cell andthe SGSN. Alternatively, before performing the switching preparationprocess of the S1 interface, the source eNB may send a response messageto the eNB serving the new cell.

In this embodiment of the present invention, the access network devicein the new cell establishes a connection with the S1 interface of thecore network device MME in the new cell by using the switchingpreparation process, or establishes a connection with the Iu or Ainterface of the SGSN, thereby ensuring service continuity of the UE inan active state.

Embodiment 4

This embodiment provides a service recovery method for a wirelesscommunication network. In this embodiment, taking that a new cell is anLTE cell as an example, an access network device in the new cell in thisembodiment is an eNB serving the new cell, that is, a new eNB. As shownin FIG. 8, this method includes:

Step 501: A UE finds an RLF, reselects a new cell, and sends an RRCre-establishment request to a new eNB.

Step 502: The new eNB receives the re-establishment request, does notfind UE context of the UE, and sends a notification message to a sourceeNB or MME to request the source eNB to perform a switching preparationprocess of an X2 and/or S1 interface.

In this step, the sending the notification message to the source eNB orMME includes: directly sending the notification message to the sourceeNB through the X2 interface; or sending the notification message to theMME through the S1 interface, and forwarding, by the MME, thenotification message to the source eNB. That is, the source eNB isinstructed to initiate the switching preparation process of the X2 or S1interface in a direct manner or in an indirect manner.

Before initiating the switching preparation process of the X2 or S1interface upon receiving the notification message, the source eNB maysend a response message to the eNB serving the new cell.

If the eNB (the new eNB) in the new cell does not know a running statusof the eNB (the source eNB) in the source cell, and the X2 interfaceexists between the new eNB and the source eNB, as shown in FIG. 8, thenotification message is sent through the X2 interface preferably, and atimer may be started at the same time. If the X2 interface does notreceive a response message within a specified time period or receives afailure message, the new eNB sends a notification message to the MMEthrough the S1 interface. The MME transfers this notification message tothe source eNB through the S1 interface to request the source eNB toinitiate the switching preparation process of the X2 and S1 interfaces.

If the MME connected to the eNB serving the new cell is different fromthat connected to the source eNB, that is, the new MME connected to thenew eNB and the source MME connected to the source eNB are not the sameentity, the new eNB sends a notification message to the new MME throughthe S1 interface, the new MME transfers this notification message to thesource MME through an S10 interface, and the source MME forwards thisnotification message to the source eNB to request the eNB to initiatethe switching preparation process of the S1 interface.

If the new cell is a UMTS or GSM cell, an access network device RNC orBSC in the new cell corresponds to the preceding eNB in the new cell,and an Iu or A interface corresponds to the preceding S1 interface. Inthis case, the RNC or BSC sends a notification message to an SGSNthrough the Iu or A interface. The SGSN sends the notification messageto the MME through an S3 interface. The MME forwards the notificationmessage to the source eNB through the S1 interface to request the sourceeNB to perform the switching preparation process of the S1 interface.Before the source eNB and the MME performs S1 interface switching, anotification response message may be sent to the RNC or BSC by beingforwarded by the SGSN. A message that is sent to the new cell after theUE detects an RLF may be an RRC re-establishment message or a cellupdate message.

In this embodiment, the access network device (eNB, RNC, or BSC) in thenew cell sends a notification message to the source eNB or the sourceMME to trigger establishment of a connection with the core networkdevice, that is, the MME or the SGSN, in the new cell, thereby ensuringservice continuity of the UE in an active state.

Embodiment 5

This embodiment provides a service recovery method for a wirelesscommunication network. In this embodiment, taking that a new cell is anLTE cell as an example, an access network device of the new cell is aneNB in the new cell, that is, a new eNB. As shown in FIG. 9, this methodincludes:

Step 701: A UE finds an RLF, reselects a new cell, and sends an RRCre-establishment request to an eNB (a new eNB) in the new cell, wherethis RRC re-establishment request carries UE context; the new eNB mayobtain the UE context from this RRC re-establishment request;alternatively, the RRC re-establishment request may carry a UEidentifier and/or S1 interface application identifiers (S1AP IDs) of asource MME and UE, where the UE identifier may be, for example, an SAETemporary Mobile Station Identifier (S-TMSI) or an International MobileStation Identifier (IMSI).

Step 702: The new eNB sends an S1 interface message, for example a pathswitch message, a handover notify message, or another S1 interfacemessage, to an MME to request for establishing an S1 connection.

Step 703: The new eNB receives an S1 interface response message from theMME.

Step 704: Send an RRC re-establishment success message to the UE.

If the S1 interface response message fails to be received from the MMEwithin a set time period in step 703, an RRC re-establishment failuremessage is sent to the UE in step 704.

Alternatively, after step 704, the method may further include:

Step 705: The MME sends an S1 interface release command to the sourceeNB to instruct the source eNB to release the S1 interface.

If the MME connected to the new eNB is different from that connected tothe source eNB, that is, the new eNB is connected to a new MME, and thesource eNB is connected to a source MME, the two MMEs transfer a messagethrough an S10 interface. The new eNB sends a message of instructing thesource eNB to release the S1 interface to the new MME through the S1interface. The new MME forwards this message to the source MME throughthe S10 interface. Then, the source MME instructs the source eNB torelease a connection of the S1 interface.

If the new cell is a UMTS or GSM cell, an access network device RNC orBSC in the new cell corresponds to the preceding eNB serving the newcell, and an Iu or A interface corresponds to the preceding S1interface. In this case, the RNC or BSC sends an Iu or A interfacenotification message, for example, a relocation complete message oranother Iu or A interface message, to a core network device SGSN in thenew cell. The SGSN sends an S3 interface message to the source MME torequest the source eNB to release the S1 interface. A message that issent to the new cell after the UE detects an RLF may be an RRCre-establishment message or a cell update message.

In this embodiment, the access network device eNB, RNC, or BSC in thenew cell establishes a connection with the MME or the SGSN through theS1 interface message or the Iu or A interface message, thereby ensuringservice continuity of the UE in an active state.

Embodiment 6

This embodiment provides a service recovery method for a wirelesscommunication network. In this embodiment, taking that a new cell is anLTE cell, an access network device in the new cell in this embodiment isan eNB serving the new cell, that is, a new eNB. As shown in FIG. 10,this method includes:

Step 901: A UE detects an RLF, reselects a new cell, and sends an RRCre-establishment request message to an eNB (a new eNB) in the new cell,where the message carries a UE identifier, such as an S-TMSI and anIMSI.

Step 902 or 902′: The new eNB sends an X2 interface message to a sourceeNB or an S1 interface message to a core network MME to request UEcontext, where the message carries the UE identifier, such as the S-TMSIand the IMSI.

Step 903 or 903′: After receiving the X2 interface message or the S1interface message, the source eNB or the MME transfers the UE context tothe new eNB according to the UE identifier, such as the S-TMSI and theIMSI.

Step 904: The new eNB sends an S1 interface message to request forestablishing an S1 interface connection with the MME, where the S1interface message may be a path switch message, a handover notifymessage, or another S1 interface message.

Step 905: The new eNB receives an S1 interface response message from theMME.

Step 906: The new eNB sends an RRC re-establishment success message tothe UE.

If the new eNB does not receive the S1 interface response message fromthe MME in step 905, an RRC re-establishment failure message is sent tothe UE in step 906.

Alternatively, after step 906, the method may further include:

Step 907: The MME sends an S1 interface release command to the sourceeNB to instruct the source eNB to release the S1 interface.

If the MME connected to the eNB serving the new cell is different fromthat connected to the source eNB, the two MMEs transfer a messagethrough an S10 interface, and the source MME instructs the source eNB torelease a connection of the S1 interface.

In step 902:

If the eNB (the new eNB) in the new cell does not know a running statusof the eNB (the source eNB) in a source cell, and an X2 interfaceexists, an X2 interface request message may be sent first to request thesource eNB to transfer the UE context, and a timer may be started at thesame time. If the X2 interface does not receive a response messagewithin a specified time period or receives a failure message, the neweNB sends an S1 interface request message to the MME to request the MMEto transfer the UE context. The request message carriers the UEidentifier, such as the S-TMSI and the IMSI.

If the MME connected to the eNB serving the new cell is different fromthat connected to the source eNB, that is, the new eNB is connected to anew MME, and the source eNB is connected to a source MME, the two MMEstransfer a message through the S10 interface, the new MME transfers arequest message that includes the UE identifier, such as the S-TMSI andthe IMSI, to the source MME through the S10 interface to request thesource MME to transfer the UE context, or the source MME forwards therequest message to the source eNB to request the source eNB to transferthe UE context.

If the new cell is a UMTS or GSM cell, an access network device RNC orBSC in the new cell corresponds to the preceding eNB in the new cell,and an Iu or A interface corresponds to the preceding S1 interface, theRNC or BSC sends an Iu or A interface request message to a core networkdevice SGSN in the new cell. The SGSN sends the request message to theMME through an S3 interface to request the MME to transfer the UEcontext; or, after receiving the request message, the MME sends therequest message to the eNB to request the eNB to send the UE context.

If the new cell is a UMTS or GSM cell, the Iu or A interface message,such as a relocation complete message and another Iu or A interfacemessage, corresponds to the preceding path switch message, handovernotify message, or another S1 interface message. In addition, a messagethat is sent to the new cell after the UE detects an RLF may be an RRCre-establishment message or a cell update message.

In this embodiment, the access network device in the new cellestablishes a connection with the MME or the SGSN through the S1interface message or the Iu or A interface message, thereby ensuringservice continuity of the UE in an active state.

It may be understandable to those skilled in the art that all or part ofthe steps in the methods of the foregoing embodiments may be performedthrough relevant hardware instructed by a program. The program may bestored in a computer-readable storage medium such as a Read Only Memory(ROM), a Random Access Memory (RAM), a magnetic disk, and a CompactDisk-Read Only Memory (CD-ROM).

Embodiment 7

This embodiment provides a service recovery apparatus 200 for a wirelesscommunication network. As shown in FIG. 11, the apparatus includes: areceiving unit 210, an RRC establishing unit 230, and a processing unit240. The receiving unit 210 receives an RRC re-establishment request ora cell update message from a UE; the RRC establishing unit 230 performsan RRC establishment process that is initiated by an NAS of the UE whenthe RRC re-establishment or the cell update fails; the processing unit240 sends an initial UE message to a core network device when the RRCestablishment process is complete.

In another embodiment of the present invention, as shown in FIG. 12, thepreceding apparatus 200 may further include: a context establishing unit250, configured to receive an initial context establishment request fromthe core network device, and send a context establishment response tothe core network device. Alternatively, this apparatus may furtherinclude a failure responding unit 220, configured to send an RRCre-establishment failure message or a cell update failure message to theUE when the RRC re-establishment request or the cell update message doesnot carry context information of the UE.

Embodiment 8

This embodiment of the present invention provides a service recoveryapparatus 300 for a wireless communication network. As shown in FIG. 13,this apparatus includes: a receiving unit 310 and a sending unit 340.The receiving unit 310 receives an RRC re-establishment request or acell update message from a UE; and the sending unit 340 sends anotification message to a source access network device to request thesource access network device to initiate a switching preparation processof an X2 and/or S1 interface when context information of the UE cannotbe obtained.

In another embodiment of the present invention, as shown in FIG. 14, theapparatus 300 may further include: a failure responding unit 320 and anRRC establishing unit 330. The failure responding unit 320 sends an RRCre-establishment failure message or a cell update failure message to theUE when context information of the UE cannot be obtained; and the RRCestablishing unit 330 performs an RRC establishment process that isinitiated by an NAS of the UE.

Further, the sending unit 340 is further configured to send anotification message to the source access network device through an X2interface; and send the notification message to a source core networkdevice for the source core network device to forward the notificationmessage to the source access network device when a notification responsemessage fails to be received within a set time period or when a failuremessage is received; or the sending unit 340 is further configured tosend the notification message to the source core network device for thesource core network device to forward the notification message to thesource access network device.

Embodiment 9

This embodiment provides a service recovery apparatus 400 for a wirelesscommunication network. As shown in FIG. 15, this apparatus includes: areceiving unit 410, an obtaining unit 420, and a sending unit 430.

The receiving unit 410 receives an RRC re-establishment request or acell update message from a UE, where the RRC re-establishment request orthe cell update message carries context information of the UE and/or aUE identifier; the obtaining unit 420 obtains the context information ofthe UE; and the sending unit 430 sends a notification message to a corenetwork device to request for establishing a connection with the corenetwork device.

Specifically, the obtaining unit 420 is further configured to obtain thecontext information of the UE from the RRC re-establishment request orthe cell update message when the RRC re-establishment request or thecell update message carries the context information of the UE; or, whenthe RRC re-establishment request or the cell update message does notcarry the context information of the UE, send a request message to asource access network device or a source core network device to requestthe context information of the UE, where the request message carries theUE identifier.

Further specifically, when the RRC re-establishment request or the cellupdate message does not carry the context information of the UE, theobtaining unit 420 is further configured to send the request message tothe source access network device through an X2 interface; and send therequest message to the source core network device when a notificationresponse message fails to be received within a set time period or afailure message is received.

In the preceding embodiment of the present invention, the servicerecovery apparatus for a wireless communication network may be an eNB inan LTE system, an RNC in a UMTS or a GSM system, or a BSC in the UMTS orthe GSM system.

An embodiment of the present invention provides a service recoverysystem for a wireless communication network. The system may implementthe service recovery methods for a wireless communication network in thefirst to sixth embodiments. The system includes the service recoveryapparatus for a wireless communication network provided in the seventh,eighth, or ninth embodiment and a core network device.

The preceding embodiments further describe the purpose, technicalsolutions, and beneficial effects of the present invention. It can beunderstood that the protection scope of the present invention is notconfined to the preceding embodiments of the present invention. Theprotection scope of the present invention is intended to cover all themodifications, equivalent replacements, and improvements provided thatthey fall in the scope of the idea and principles of the presentinvention.

What is claimed is:
 1. A service recovery method comprising: receiving,by a target base station, a radio resource control (RRC)re-establishment request from a terminal; and sending, by the targetbase station, an indication message, in response of the RRCreestablishment request, indicating a radio link failure to a sourcebase station to trigger the source base station with self-determinationto initiate a handover preparation procedure between the source basestation and the target base station, wherein the terminal remains in anactive state.
 2. The method according to claim 1, wherein sendingfurther comprises sending, by the target base station, the indicationmessage to the source base station to trigger the source base station toinitiate the handover preparation procedure when the source base stationmatches context information of the terminal.
 3. The method according toclaim 1, further comprising: sending an RRC re-establishment failuremessage to the terminal; and performing an RRC establishment processthat is triggered by a non-access-stratum of the terminal.
 4. The methodaccording to claim 3, wherein, in the RRC establishment process, anindication of the terminal carries a cause value to indicate a releasecause of a RRC connection failure.
 5. An apparatus comprising: areceiver configured to receive a radio resource control (RRC)re-establishment request from a terminal; and a transmitter configuredto send an indication message, in response to a RRC re-establishmentrequest, indicating a radio link failure to a source base station totrigger the source base station with self-determination to initiate ahandover preparation procedure between the source base station and atarget base station wherein the terminal remains in an active state. 6.The apparatus according to claim 5, wherein the transmitter is furtherconfigured to send the indication message to the source base station totrigger the source base station to initiate the handover preparationprocedure when the source base station matches context information ofthe terminal.
 7. The apparatus according to claim 5, further comprisinga processor configured to: send an RRC re-establishment failure messageto the terminal; and perform an RRC establishment process that istriggered by a non-access-stratum of the terminal.
 8. The apparatusaccording to claim 7, wherein, in the RRC establishment process, anindication of the terminal carries a cause value to indicate a releasecause of a RRC connection failure.
 9. A service recovery methodcomprising: receiving, by a source base station, an indication messageindicating a radio link failure sent from a target base station; andinitiating with self-determination, by the source base station, ahandover preparation procedure between the source base station and thetarget base station triggered by the indication message.
 10. The methodaccording to claim 9, wherein initiating further comprises initiating,by the source base station, the handover preparation procedure triggeredby the indication message when the source base station matches contextinformation of a terminal which remains in an active state.
 11. Themethod according to claim 10, wherein the indication message correspondsto a radio resource control (RRC) re-establishment request from theterminal.
 12. An apparatus comprising: a receiver configured to receivean indication message indicating a radio link failure sent from a targetbase station; and a processor configured to initiate withself-determination a handover preparation procedure between theapparatus and the target base station triggered by the indicationmessage.
 13. The apparatus according to claim 12, wherein the processoris further configured to initiate the handover preparation proceduretriggered by the indication message when the apparatus matches contextinformation of a terminal which remains in an active state.
 14. Theapparatus according to claim 13, wherein the indication messagecorresponds to a radio resource control (RRC) re-establishment requestfrom the terminal.